While battery-electric and plug-in hybrid cars have had much of the spotlight to themselves for the past four years, we're going to be hearing a lot more about hydrogen fuel-cell cars over the next few.

And a new study just released by the University of California--Davis suggests that we are "tantalizingly close to the beginning of a hydrogen transition."

That's the cost that would make hydrogen fuel no more expensive than gasoline, measured by cents per mile traveled.

To get there, the study recommends targeted investment of $100 million to $200 million to establish clusters of 100 hydrogen fueling stations that can support up to a total of 50,000 fuel-cell vehicles.

Those should be, the study suggests, in Southern California (where the state has already committed funds through 2025 for up to 100 stations), Germany, and Japan.

The challenge is that over the next five years, total volumes of hydrogen fuel cell cars in California are likely to be just a small fraction of that number--since their manufacturers will be using them largely as compliance cars to meet the state's stringent zero-emission vehicle sales mandate.

The study suggests it will take five years to get to a hydrogen-fuel cost of $7.50 per kg, and 12 years to make further progress to $6 per kg--during which time the fuel efficiency of gasoline and diesel cars will have risen, lowering their own cost per mile substantially.

If you like fracking...

The second concern is that affordable hydrogen fuel is predicated on a continued to supply of inexpensive domestic natural gas as a feedstock.

"The next three to four years will be critical for determining whether hydrogen vehicles are just a few years behind electric vehicles," the study cautions, "rather than decades."

The study's title is posed as a question, which would seem to suggest serious concern over whether that will, in fact, happen.

But you will likely soon hear quite a lot about the benefits of hydrogen fuel-cell vehicles, why they have all the benefits of battery-electrics without any of the range anxiety, and why they're right around the corner.

This should be quite interesting to watch as it unfolds. Make some popcorn, buckle your seat belts, and settle in for the ride.